Xerographic developer seal and process



July 25, 1967 c. F. ROTH, JR

XEROGRAPHIC DEVELOPER SEAL AND PROCESS 5 Sheets-Sheet 1 Filed March 1,1965 INVENTOR.

CHARLES F. ROTH, JR. BY?

ATTQRNEVS July 25, 1967 c. F. ROTH, JR 3,332,328

XEROGRAPHIC DEVELOPER SEAL AND PROCESS Filed March 1, 1965 5 heets-Sheet//////4//////////////////////////////////// )(//////////)V///////////MOT-l //6J Hf!!! INVENTOR.

CHARLES F. ROTH, JR.

BY Wa' 9 A T TORNEYS Jilly 25, 1967 c. F. ROTH, JR 3,332,328

XEROGRAPHIC DEVELOPER SEAL AND PROCESS Filed March 1, 1965 3Sheets-Sheet 3 Q Mmm MIHIHHIHIP r 941 E/////////////////////fi/////////////////////fi INVENTOR. CHARLES E RI8Y7 AT T R S United States Patent 0 ork Filed Mar. 1, 1965, Ser. No.436,173 4 Claims. (Cl. 951.7)

This invention relates to an improved xerographic developing apparatusand process and, in particular, to improvements in cascade developmentof xerographic lmages.

In the process of xerography, an electrostatic charge in imageconfiguration of original copy is produced on the surface of aphotoconductive drum. This latent electrostatic image on thephotoconductive surface is developed with a powder material referred toherein as toner. Toner normally consists of a finely divided pigmentedresin attractable by the electrostatic forces to the photoconductivesurface. The electrostatic charge on the photoconductive surface holdsthe toner on the photoconductive surface in image areas, thus, producinga developed powder image of the copy being reproduced.

One form of development system for developing the latent electrostaticimage with toner or powder is commonly referred to as cascadedeveloping. Cascade development is a two component system wherein smallglass beads are mixed with the toner to act as a carrier for the tonermaterial. The glass beads provide mechanical control of the toner and;when agitated with the toner, it provides a triboelectric charge whichholds the toner on the surface of the glass bead. The combination ofglass beads or carrier and toner is referred to as developer ordeveloper material. When the developer material is cascaded over thesurface of a xerographic plate containing an electrostatic latent imagethereon, the toner, which is adhering to the carrier by triboelectricforces, is attracted away from the carrier by the stronger electrostaticcharges and is held on the surface of the xerographic plate. Inconventional cascade development systems, the carrier continues tocascade across the surface of the xerographic plate back into a hopperor supply bin wherein it is again agitated with toner material andrecascaded over the surface of the xerographic plate.

In the reproduction of semi-micro images, such as, for example, imageswhich are reduced in size from 2 /2 to 3 times their original size priorto reproduction, it is necessary to use a carrier bead which isconsiderably smaller than the carrier bead normally used in cascadedeveloping. The carrier beads used in semi-mirco reproduction work areso small that the force of gravity which carries the bead across thesurface of the xerographic plate and back into the developer bin, is insome instances less than the attractive forces from the electrostaticcharge on the plate surface. Thus, some of the glass beads tend toadhere to the surface of the plate interfering with the developmentprocess and the transfer of the powder image to support materialsurfaces. In automatic xerographic machines wherein the xerographicplate is in the form of a rotating drum, the carrier beads which adhereto the surface of the xerographic plate are carried out of thedevelopment system and into the mechanical apparatus of the machine.These carrier beads cannot be scraped from the surface of thexerographic drum without either upsetting the powder image loosely heldthereon or damaging the photo-conductive surface of the drum.

It is therefore the primary object of this invention to improvexerographic developing apparatus by sweeping the xerographic surfacewithout disrupting the powder image thereon.

It is also an object of this invention to improve cascade 3,332,328Patented July 25, 1967 development systems to permit the use of carrierparticles so small that the force of gravity is insuflicient to separatethe carrier particle from the xerographic surface.

It is also an object of this invention to improve xerographic cascadedevelopment systems by sweeping a current of air over the xerographicsurface with an intensity sufficient to separate carrier beads from thexerographic surface without disrupting the powder image thereon.

These and other objects of this invention are attained by means of anair knife positioned adjacent to the xerographic drum at the point wherethe xerographic drum emerges from the development system and a source ofair which is directed by the air knife against the surface of thexerographic drum at the outlet of the development system to therebydeflect carrier beads off the surface of the drum back into thedevelopment system.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic side view of paratus utilizing the presentinvention;

FIG. 2 is a pneumatic system of the xerographic machine shown in FIG. 1;

FIG. 3 is an enlarged detailed view of the xerographic drum developmentsystem and air knife shown in FIG. 1.

The present invention is suitable for use in automatic xerographicmachines of the type disclosed in copending application Ser. No.436,168, filed Mar. 1, 1965, in the name of Thomas H. Galster, Allen M.Hitchcock and Gordon P. Taillie. A schematic representation of thefunctions of that machine are shown here in FIG. 1.

As seen in FIG. 1, a rotatable xerographic drum 10 is mounted forrotation on a shaft 12. The drum rotates about the shaft 12 in thedirection indicated by the arrow and passes a charging station generallyindicated as 14 wherein a corotron 16, connected to a suitable powersource not shown, places a uniform electrostatic charge on the surfaceof the xerographic drum. The drum rotates past an exposure station 18wherein light images of copy to be reproduced discharge theelectrostatic charge on the drum surface and produces a latentelectrostatic image of the copy being reproduced on the drum surface.The drum then rotates past a developer station, enerally indicated as20, wherein a developer mechanism, described in detail below, developsthe latent electrostatic image into a powder image. After theelectrostatic image is developed, a pretransfer corotron 22 places anelectrostatic charge on the surface of the drum to loosen the powderimage for transfer purposes. The drum then rotates past a transferstation 24 wherein the powder image is transferred to a suitable supportmaterial surface by means of a transfer corotron 26 which places asuitable electrostatic charge on the back surface of the supportmaterial to attract the powder from the xerographic drum to the supportmaterial. The support material is then transported past a fusing station28 wherein the support material and the powder image thereon are exposedto rays from a flash fuser 30 which heats the powder causing it tocoalesce and bond to the surface of the support material. Thexerographic drum rotates past a cleaning station 32 wherein residualtoner material remaining on the surface of the drum is cleaned therefromby means of a rotating brush 34.

In the apparatus shown either images of original copy reduced to 2 /2 to3 times its size may be reproduced on data processing cards orpreviously reduced images on data processing cards may be reproducedonto other data processing cards. Documents which are to be reduced andcopied on data processing cards are placed on a document a xerographicap- 3 tray 36. The tray 36 is mounted on a pair of rollers 38 on a track48. With the document to be reproduced on the tray 36, the tray is movedforward towards a scanning station 42. With the tray 36 in the forwardposition, the document is picked up by a belt conveyor 44 and a feedroller 46 in a manner described in detail in the abovecited copendingapplication Ser. No. 436,168. The document is held on conveyor 44 bymeans of a vacuumproduced in a manifold 48 which produces a suctionthrough a series of openings in the manifold and correspondingperforations in the surface of the belts in the conveyor 44. Theconveyor 44 carries the documents past the scanning station 42 wherein apair of lamps LMP-l illuminate incremental areas of the surface of thedocument. The illuminated areas of the document are reflected by amirror 50 through a reducing lens 52 to the surface of the xerographicdrum at exposure station 18. The movement of the conveyor 44 issynchronized with the movement of the drum 12 so that the image isplaced on the drum surface with the proper size reduction. The conveyor44 then carries the document around a main drive roller 54 by means of aseries of resilient rollers 56 rotatably mounted and in surface contactwith the belts of the conveyor 44 as they extend around the roller 54.When the document emerges from the bands 56, it is again held on thebelts of the conveyor 44 by means of a vacuum produced in manifold 48.The document is carried forward beyond the end of the manifold 48 where,with the suction released, it tends to drop away from the conveyor 44and is deflected downward by a plate 60 into a receiving tray 62.

When it is desirable to reproduce images from data processing cards, aseries of cards 64 containing xerographic images thereon are stacked ina conventional card feeding hopper 67 and fed onto a card conveyorsystem which is similar to the conveyor system 44. The card conveyor isnot shown, but is a vacuum conveyor which carries the cards past ascanning station similar to the scanning station 42 and deposits thecards into a card receiving hopper. Illuminated portions of the card aredeflected upwards into a mirror 66 which directs the images through alens 68 to a mirror 78 which directs the image onto the surface of thexerographic drum at the exposure station 18.

Images reproduced on the surface of the xerographic drum are transferredto blank data processing cards 72 which are fed from a conventional cardfeeding hopper 74 to a roller type conveyor system 76. The conveyor 76consists .of a series of rollers '78 which feeds the cards past a rotarycard timing device into surface contact with the xerographic drum 11).

The cards '72 are forced into surface contact with the drum by means ofa series of bands 82 which are held in surface contact with the drum 10by means of a pair of rollers 84 and are moved at the same speed as theperiphery of the xerographic drum'ltl. The bands 82 force a the card 72into surface contact with the xerographic drum at the point at which thecorotron 26 places an electrostatic charge on the back of the card totransfer the powder image from the drum surface to the card surface. Asthe card emerges from the bands 82, it is peeled off the surface of thedrum by means of a blade 86 which extends into an undercut portion ofthe xerographic drum, as shown in FIG. 3. The bands 82 are held intension by a pair of spring loaded rollers 88 and the entire transferassembly 24 is movable into and out of contact with the drum by means ofa cam 90 which may be rotated against a cam follower 92 mounted on apivot arm 94 and supporting the corotron 26 and frame plates 96 on whichthe rollers 84 are mounted.

When the card 72 containing a transferred powder image is deflected fromthe xerographic drum 10 by the blade 86, it is held on a conveyor 98 bythe suction produced in a vacuum manifold 102. The conveyor 98 carriesthe card past the fuser station 28 wherein the powder image is heated toa point where it coalesces and bonds to the card surface. The cardcontaining the fused image is then transferred to a second conveyor 104which is also a vacuum conveyor having a vacuum manifold 106. A thirdvacuum conveyor 108, having a vacuum manifold 111 receives the card fromthe conveyor 104 and transports it to a card receiving hopper 112 Whereit is deposited until such time as the machine operator removes it.

FIG. 2 shows the pneumatic system for the entire machine shown inFIG. 1. A first exhaust fan 114 exhausts air from the vacuum manifold102 through line 116, the fuser 30 through a pair of lines 118 and fromthe housing of the brush cleaner 34 at the drum cleaning station 32through line 119. A second fan 120 exhausts air from the manifolds 106and 110 through hoses 121, 122 and 124. A third fan 126 exhausts airfrom the manifold 48 in the document conveyor 44 and the manifold 128located in the card conveyor associated with the card feed hopper 66through hoses 129, 130, 132 and 134.

A motor MOT-1 drives an air compressor 136 which supplies air underpressure to the air knife, generally indicated as 138, through air line140. The air knife 138 is seen in section in FIG. 3 and consists of atubular inlet section 142 which is connected to the air line 140 and hasan opening 144 permitting passage of the air to an elongated taperednozzle 146. The nozzle 146 is tapered from the tubular inlet section 142down towards the xerographic drum with the smaller end being openedacross the width of the drum surface. The small open end 148 ispositioned adjacent the surface of the xerographic drum 10 at the pointwhere the surface of the drum emerges from the developer housing 150.

As seen in FIG. 1, the developer housing 150 contains a supply ofdeveloper material 152 consisting of toner material and small carrierbeads. The developer material 152 is located in the bottom of thehousing 150 providing a supply of fresh developer material forcontinuous bucket conveyor 154. As the xerographic drum 10 rotates, theconveyor 154 rotates its buckets through the developer material 152 inthe bottom of the housing and conveys the material to the top of thehousing 150 wherein it discharges the developer material down onto abaflle 156. The baflle 156 directs the developer material onto thesurface of the xerographic drum where it is cascaded over the drumsurface and directed back towards the bottom of the housing 150 by asecond baffle 158. During passage over the surface of the xerographicdrum, the developer material leaves toner material in the electrostaticimage areas, and the carrier material is theoretically directed backtowards the sump portion of the housing 150 where it is mixed withadditional toner material by the agitation of the conveyor 154. However,because of the size of the carrier particles, the electrostatic chargeon the drum surface is suflicient to hold some of the carrier materialon the drum, that is, the forces produced by the electrostatic charge onthe carrier are greater than the force of gravity on the individualcarrier particles, thus, the particles adhere to the drum surface. Thebaflle 158 and the edge of the developer housing 150 cannot be incontact with the surface of the xerographic drum or else the carrierparticles which adhere to the drum surface will lodge between the baflieof the developer housing and scratch the surface of the xerographicdrum. Further, the baffle 158 and the developer housing 150 should notin any case touch or disrupt the powder image on the surface of thexerographic drum. Therefore, any of the carrier particles which doadhere to the electrostatic charge on the drum surface tend to rotateout of the developer housing along with the rotation of the drum 10.Particles adhering to the drum outside the development area interferewith effective transfer of the powder image to the support materialsurface and also tend to become lodged in the moving parts of theoverall machine.

The air knife 138 is directed at an angle against the drum surface atthe point where the surface of the drum emerges from the developerhousing 150. Air under pressure entering the inlet 42 of the air knife138 is directed by the nozzle 146 towards the open end of the nozzle 148and against the drum surface at the point where the carrier beads tendto leave the development area. The force of the air from the nozzle 146is sufficient to separate the carrier particles from the surface of thedrum and deflect them back into the developer housing 150. The force ofthe air does not upset the powder image on the drum or in any wayinterfere with the effective development and transfer of images.

The carrier beads used in the developer are in the 250-450 micron sizerange. This size bead will be effectively deflected back into thedeveloper housing by an air stream from the air knife 138 which istraveling at approximately 550 inches per second. With an air knifehaving an opening inch wide and 5 inches long, the air pressure at theopening is one-half p.s.i. having an air velocity of 550 inches persecond, and 3 cubic feet air per minute are passed through the openinginto the developer housing. The air enters the developer housing andemerges therefrom through the normal openings in the housing. Thedeveloper beads are deposited in the bottom of the housing for reuse inthe development process.

While the invention has been described with reference to the structuredisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the purpose of the improvements or the scope of thefollowing claims.

What is claimed is:

1. In a Xerographic machine of the type utilizing a development systemwherein a powder image is developed on a xerographic plate by cascadingcarrier particles and toner material over the surface of the Xerographicplate, apparatus for removing those carrier particles adhering to thesurface of the Xerographic plate and depositing them into a developersump comprising in combination a housing enclosing at least a portion ofthe Xerographic plate,

conveyor means disposed within said housing for cascading carrierparticles and toner material across the plate surface,

nozzle means extending across the plate surface and positioned to directa stream at an angle against the plate surface, toward a narrow openingdefined by the lower boundary of said housing and said plate surface,

and means to supply air to the nozzle means under a pressure sufficientto produce a velocity of air which,

when directed against the plate and into said narrow opening, willseparate those carrier particles held on the plate by electrostaticcharge from the plate surface and deposit them into a developer sumpformed at the bottom of said housing without disrupting the powder imageon the plate surface.

2. In a xerographic machine wherein an electrostatic image is developedon the surface of a rotating drum by cascading carrier particles andtoner material located in a developer housing over the surface of thexerographic drum, apparatus for removing those carrier particlesadhering to the surface of the Xerographic drum and depositing them intoa developer sum formed in the bottom of the housing comprising incombination a xerographic dru m journaled for rotational movement,

a housing enclosing at least a portion of the xerographic drum,

drive means for rotating said drum,

conveyor means disposed within said housing for cascading carrierparticles and toner material across the surface of said xerographicdrum,

nozzle means positioned adjacent to the Xerographic drum and extendingacross the drum surface,

the nozzle means having an opening directed at the junction of the drumsurface with the lower boundary of the developer housing,

and means to supply air to the nozzle means under pressure so that airpassing through the nozzle opening will deflect those carrier particlesheld on the drum surface by electrostatic charge back into a sump formedin the bottom of the developer housing,

the air supply being sufficient to produce air velocity at the openingthat will deflect carrier size particles but will not disrupt tonermaterial being held on the drum by electrostatic charges. 3. The processof reproducing minified images Xerographically comprising exposing acharged photoconductive insulating member to a minified pattern of lightand shadow in accordance with the image to be reproduced,

cascading a two-component developer mixture made up of tiny carrierbeads and electroscopic toner material across the exposed surface todevelop a high quality powder image,

selectively removing carrier lbeads accidentally sticking to the exposedsurface by positioning an air stream on them directed toward a narrowOpening defined by the developer supply and the insulating member todeposit them into a developer sump, and transferring the powder image toa support material.

4. The process according to claim 3 wherein the size of the carrierbeads ranges from about 250 to about 450 microns.

References Cited UNITED STATES PATENTS 2,573,881 11/1951 Walkup et al.118-637 X 3,063,868 11/1'962 Brandsma et al. 1l8-63 X 3,100,426 8/1963Kaprelian 1l8637 X 3,196,832 7/1965 Zin 118637 CHARLES A. WILLMUTH,Primary Examiner. PETER FELDMAN, Assistant Examiner.

1. IN A XEROGRAPHIC MACHINE OF THE TYPE UTILIZING A DEVELOPMENT SYSTEMWHEREIN A POWDER IMAGE IS DEVELOPED ON A XEROGRAPHIC PLATE BY CASCADINGCARRIER PARTICLES AND TONER MATERIAL OVER THE SURFACE OF THE XEROGRAPHICPLATE, APPARATUS FOR REMOVING THOSE CARRIER PARTICLES ADHERING TO THESURFACE OF THE XEROGRAPHIC PLATE AND DEPOSITING THEM INTO A DEVELOPERSUMP COMPRISING IN COMBINATION A HOUSING ENCLOSING AT LEAST A PORTION OFTHE XEROGRAPHIC PLATE, CONVEYOR MEANS DISPOSED WITHIN SAID HOUSING FORCASCADING CARRIER PARTICLES AND TONER MATERIAL ACROSS THE PLATE SURFACE,NOZZLE MEANS EXTENDING ACROSS THE PLATE SURFACE AND POSITIONED TO DIRECTA STREAM AT AN ANGLE AGAINST THE PLATE SURFACE, TOWARD A NARROW OPENINGDEFINED BY THE LOWER BOUNDARY OF SAID HOUSING AND SAID PLATE SURFACE,AND MEANS SUPPLY AIR TO THE NOZZLE MEANS UNDER A PRESSURE SUFFICIENT TOPRODUCE A VELOCITY OF AIR WHICH, WHEN DIRECTED AGAINST THE PLATE ANDINTO SAID NARROW OPENING, WILL SEPARATE THOSE CARRIER PARTICLES HELD ONTHE PLATE BY ELECTROSTATIC CHARGE FROM THE PLATE SURFACE AND DEPOSITTHEM INTO A DEVELOPER SUMP FORMED AT THE BOTTOM OF SAID HOUSING WITHOUTDISRUPTING THE POWDER IMAGE ON THE PLATE SURFACE.
 3. THE PROCESS OFREPRODUCING MINIFIED IMAGES XEROGRAPHICALLY COMPRISING EXPOSING ACHARGED PHOTOCONDUCTIVE INSULATING MEMBER TO A MINIFIED PATTERN OF LIGHTAND SHADOW IN ACCORDANCE WITH THE IMAGE TO BE REPRRODUCED CASCADING ATWO-COMPONENT DEVELOPER MIXTURE MADE UP OF TINY CARRIER BEADS ANDELECTROSCOPIC TONER MATERIAL ACROSS THE EXPOSED SURFACE TO DEVELOP AHIGH QUALITY POWDER IMAGE, SELECTIVELY REMOVING CARRIER BEADSACCIDENTALLY STICKING TO THE EXPOSED SURFACE BY POSITIONING AN AIRSTREAM ON THEM DIRECTED TOWARD A NARROW OPENING DEFINED BY THE DEVELOPERSUPPLY AND THE INSULATING MEMBER TO DEPOSIT THEM INTO A DEVELOPER SUMP,AND TRANSFERRING THE POWDER IMAGE TO A SUPPORT MATERIAL.